Because it's turing complete.
A program that reads 2 numbers, adds them and outputs the result.
In solidity this would be written as:
function add(uint256 a, uint256 b) returns (uint256) {
return a + b;
}Look how long this is. Unacceptable!
The same program written in brainfuck would be:
,>,<[->+<]>.uint8 a = 4;
uint8 b = 5;
uint256 mem_size = 2;
uint256 output_size = 1;
bytes memory input = abi.encodePacked(a, b);
bytes memory result = bf.execute(",>,<[->+<]>.", input, mem_size, output_size);
console.logBytes(result);$ forge script ./script/Brainfuck.s.sol
Script ran successfully.
Gas used: 56108
== Logs ==
0x09